Abstract
The central aim of the nutrition sciences is to understand how nutrition impacts health. One problem supposedly plaguing this endeavor is nutritionism—a ‘reductive’ focus on the role of nutrient composition or isolated nutrients (e.g., macronutrients or vitamins) for explaining a food’s effects on health (Scrinis 2008; 2013). Methodologically ‘reducing’ foods to nutrients can foster adversarial debates about the purported health effects of isolated nutrients, obscure the complexity of food-organism interactions, and distort how nutrients produce different outcomes in the context of foods, processing techniques, or dietary patterns. Anti-reductionist critiques, most of which claim that foods or dietary patterns should be the fundamental explanatory levels, permeate nutrition research (Messina et al. 2001; Zeisel et al. 2001; Hoffmann 2003; Jacobs and Tapsell 2008; Fardet and Rock 2014; 2018; 2020; Mayne, Playdon, and Rock 2016; Mozaffarian, Rosenberg, and Uauy 2018; Rees 2019; Moughan 2020; Campbell 2021). Moreover, the claim that nutritionism is the “dominant ideology” is entering philosophy (Siipi 2013; Borghini, Piras, and Serini 2021). Amidst calls to reform nutrition research (Ioannidis 2013; 2018; Mozaffarian and Forouhi 2018; Hall 2020), this presentation contributes by clarifying whether the problem raised by nutritionism is less about which level is fundamental (nutrients vs. foods), and more about which level(s) provide adequate explanations of what in nutrition impacts health. 1) For instance, are explanations that aim to link the nutrients in foods or dietary patterns to specific health outcomes inherently flawed? 2) Relatedly, can nutrient-level research elucidate causal mechanisms that are often obscured in highly complex food- or diet-based investigations? 3) Moreover, can nutrients explain variations in organismal feeding behaviors, explaining why organisms select their foods? While the complexity of food-health interactions requires more than ‘one nutrient at a time’ approaches (Simpson, Le Couteur, and Raubenheimer 2015), answering the above questions entails evaluating whether/how nutrient-level research can generate integrative explanatory frameworks (Brigandt 2010). First, I analyze claims that nutrient reductionism could be useful if it offers mechanistic explanations that combine explanatory levels (Machamer, Darden, and Craver 2000; Ströhle and Döring 2010). For instance, nutritional ecologists propose that nutrient ratio variations, e.g., protein to carbohydrates, are the common threads among foods, meals, and diets that provide robust explanations of distinct outcomes—from metabolic regulation and biological fitness to obesity (Raubenheimer and Simpson 2016; 2019; 2020)—and of organismal feeding behaviors: organisms select foods largely based on nutrient content (Simpson and Raubenheimer 2012). Can this form of nutrient-level research offer ‘appropriate’ levels of complexity to clarify how dietary constituents interact, which properties of foods or diets reliably affect health, and the mechanisms involved (Solon-Biet et al. 2019)? I further analyze this proposal by looking at how nutrients modulate cancer risk and development (Theodoratou et al. 2017; Zitvogel, Pietrocola, and Kroemer 2017; Altea‐Manzano et al. 2020; Kanarek, Petrova, and Sabatini 2020; Salvadori and Longo 2021). Overall, I offer an epistemological evaluation of nutrient-level research and its potentially integrative explanations of what in foods and dietary patterns affects health.
